In the ecological engineering fields in Jin Hua, Zhejiang province, flora diversity was enhanced by populating the bunds and non rice habitats with sesame, Zizania and nectar rich flowering plants. This practice has clearly increased the density of parasitoids and predators (Read: Sesame on bunds). In September 2010 a field day organized by the National Agri-tech Extension Service Center (NATESC), Zhejiang Academy of Agriculture Sciences (ZAAS), the Zhejiang Provincial Bureau of Plant Protection and the Jinhua Plant Protection Station (JPPS) attracted national attention (Read: Jinhua gets national attention) .

Rana limnocharis in the field

We also observed substantial increases in frogs, particularly two species Rana limnocharis and R. nigromaculatta. Frogs are known to be excellent indicators of ecosystem health. Amphibians’ thin skins make them susceptible to environmental contaminants, particularly agricultural chemicals. Many insecticides act as endocrine disruptors, inducing feminizing effects and severely affecting populations. Amphibians are like canaries in the coal mine as indicators of toxic gases in the mines, can serve as indicators of polluted environmental conditions which can have severe health consequences. For more details see http://www.amphibianark.org/the-crisis/amphibians-as-indicators/.

As shown in Table 1 and Figure 1, the ecological engineering fields had 4 to 6 times higher frog densities than the farmers fields. The high densities of frogs may have positive effects on pest populations as they are highly effective predators. Further investigations are being carried out in ZAAS to determine its predation effects.

The high densities of frogs are strong indicators of ecosystem health of the ecological engineering fields. The ecological engineering practices of increasing flora biodiversity and reducing insecticide use seem to have encouraged the return of frog and ecosystem health in Jin Hua. Yields of the ecological engineering fields and that of the farmers’ fields were 10.01 t/ha and 10.03 t/ha, respectively.

In Zhejiang province, China rice crops are often infested with the rice black streak dwarf virus (RBSDV) transmitted by the small brown planthopper (sBPH), Laodelphax striatellus. These infected plants are usually stunted, have more tillers and darker green leaves. The RBSDV and the sBPH have multiple hosts that include maize, barley and wheat which act as source to perpetuate transmission in China.

We found that the brown planthopper (BPH), which is not a vector of the virus, survives better on RBSDV infected plants. BPH on the infected plants have significantly higher nymphal survival rates, heavier and higher egg hatchability (See Table 1).

Rice plants infected with RBSDV are stunted and have dark green leaves

Since in Zhejiang province there is usually high RBSDV infected plants in the first crop of hybrid rice, these virus infected plants can make further contributions towards the increase of BPH in the later season. A reason for BPH to have higher fitness is possibly the higher nitrogen accumulation in the leaves of the diseased plants. This is being investigated in ZAAS.

In ecological engineering fields, the bunds were replaced with flowering plants

In Chainat Rice Research Center, we used part of the farm to evaluate the impact of ecological engineering on the biodiversity of arthropods. The areas surrounding the rice fields were replaced with several species of flowering plants and vegetables to provide habitats and nectar resources to natural enemies. Another area of the farm was left as the control with no modifications to the surrounding bunds. Several ecological sampling techniques applied to record arthropod species (ecological sampling protocols). We have sorted out the samples of arthropods collected using the yellow pan traps set up for 24 hours each during the tillering, maximum tillering and maturing stages of the rice crop. The pooled data of all samples in the control and ecological engineering fields were compared.

Map of ecological engineering and control fields in Chainat Rice research Center

The arthropods were grouped into guilds or functions and the functional biodiversity analyzed using indices computed by ECOSIM (Gotelli and Entsminger 2005) and EstimateS (Colwell 2006). To avoid sample size sensitivity, rarefaction techniques were used to compute species richness. The indices that have less sample size sensitivity and with more discriminating abilities were used for comparison (Magurran 1988). Table 1 shows the biodiversity indices of the arthropod guilds of the control and ecological engineering fields and the rarefaction curves are also presented.

Yellow pan traps set up in the rice fields to record arthropods

Table 1: Comparison of arthropod biodiversity from yellow pan traps in ecological engineering and control fields in Chainat Rice Research Center. 2009.

Guilds

Biodiversity parameters

Control

Eco Eng

Herbivores

% abundance

10.4%

13.2%

Species richness, S or Esn (rarefaction)

13

13.8

Log series index alpha

4.60

5.04

Reciprocal Simpson’s (1/D)

0.16

0.16

Exp Shannon or Hill N1

7.86

8.04

Predators

% abundance

32.9%

20.9%

Species richness, S or Esn (rarefaction)

26

27.3

Log series index alpha

8.37

9.38

Reciprocal Simpson’s (1/D)

0.14

0.13

Exp Shannon or Hill N1

11.82

12.50

Parasitoids

% abundance

45.9%

13.2%

Species richness, S or Esn (rarefaction)

15.99

30

Log series index alpha

8.84

17.56

Reciprocal Simpson’s (1/D)

0.36

0.05

Exp Shannon or Hill N1

6.15

21.2

Others

% abundance

22.7%

40.7%

Species richness, S or Esn (rarefaction)

6

5.67

Log series index alpha

1.12

1.23

Reciprocal Simpson’s (1/D)

0.42

0.57

Exp Shannon or Hill N1

2.89

2.38

Biodiversity of herbivores, predators and others in the control and ecological engineering plots were rather similar. For the parasitoids, species richness S (after rarefaction) increased significantly from 16 to 30. There were more hymenopteran species in the ecological engineering plot than in the control.

Rarefaction curves of parasitoids of samples collected in ecological engineering and control fields in Chainat Rice Research Center.

Changes in parasitoid biodiversity is further evident from the diversity index, alpha, of the log series which has good discriminant ability of richness (Taylor 1998). Biodiversity doubled in the ecological engineering fields (17.6 and 8.8). There are similar increases in the diversity index, exponential Shannon or Hill’s N1 which also reflects richness, from 6.2 to 21.2.

A workshop that discusses the issues around host-plant resistance (HPR) in the management of brown- and white-backed hoppers in Asia has begun today at IRRI. Scientists concerned about the current planthopper outbreaks that are occurring right throughout the region will focus on the causes of the outbreaks, the context for IPM and possibilities of HPR as a component of management strategies. Participants in the workshop are mainly from regions where hoppers are now a serious issue; based on their experiences and knowledge of the hopper problems, these participants aim to improve communication between scientists by defining concepts that are key components to management and determining the best strategies going forward.

In the summer-autumn crop season this year, farmers in Bac Giang province in Northern Vietnam observed yellowing symptoms in their rice crops about a month after high populations of green leafhoppers (GLH) were observed (Figure 1). The syndrome seemed similar to rice tungro virus disease, which is prevalent in Southeast Asia, However, scientists from Hanoi Agricultural University and Plant Protection Research Institute using RT-PCR identified the disease to be caused by the rice transitory yellowing virus (RTYV). The virus is known to be transmitted by GLH. RTYV (also known as rice yellow stunt virus) was first found in 1965 in Taiwan and in Southern and Central China, and later reported in Japan and Thailand. In 1985 the diseases were also reported in Vietnam and Laos.

Rice plants infected with RTYV show leaf yellowing, reduced tillering and mild stunting. Later, infected plants develop normal looking leaves and may appear healthy (thus, the name “transitory”) but symptoms may reappear after the temporary recovery. The virus is transmitted in a persistent manner by Nephotettix cincticeps, N. nigropictus and N. virescens. The virus propagates in the vectors, but it is not transmitted via eggs.

A report by the International Trade Studies Center at the University of the Thai Chamber of Commerce (UTCC) says that in the next 10 years Thailand will continuously lose market share and competitiveness to Vietnam in ASEAN and other markets. One of the contributing factors to Vietnam rice production success is the implementation of the “Three Reductions, Three Gains” policy that was developed by scientists from Vietnam’s Ministry of Agriculture and Rural Development (MARD), Visayas State University (VSU) and IRRI. News of the report was featured in Thai newspapers, The Nation and Bangkok Post.

The Three Reductions, Three Gains poster

Locally known as “Ba Giam Ba Tang”, the program was launched in March 2003 in Can Tho city. In 2006 the Minister of Agriculture, Dr Cao Duc Phat made “Ba Giam Ba Tang”, a national policy and provided support for its implementation in all provinces. The program was developed from the success of an earlier campaign to motivate farmers to stop early season insecticide use (no early spray or NES) which reduced farmers sprays by 53%. (Read: No early spray campaign). Ba Giam, Ba Tang incorporated NES together with guidelines to reduced seed and fertilizer rates and used multi media campaign materials like leaflets, posters, radio and TV to reach millions of farmers. The campaign successfully reduced famers’ insecticide use by 33%, their seed and fertilizer rates by 11% and 7%, respectively (Read: Motivating farmers with 3R3G).

Rapid adoption of Ba Giam Ba Tang followed after the campaign and in some provinces, like An Giang, adoption rate reached 70% in 3 year (Read: Adoption of 3R3G). Prior to the campaign MARD, VSU and IRRI scientists conducted farmer participatory evaluations and found that farms practicing 3 reductions have higher profits, averaging US$ 35 to US$58 per ha per season (Read: Farmer participatory evaluation). In addition the insecticide reduction reduced the farmers’ vulnerability to planthopper outbreaks and contributed to environmental conservation. MARD officials attributed the widespread adoption of 3 reductions to the Vietnam’s bumper crop in 2009 (Read: Vietnam’s bumper crop).

The report predicts that in 2020 Thailand’s rice export will drop by 14% to 8.6 million tons per annum while Vietnam’s export will increase by 25% to 7.5 million tons. There is concern that Thailand’s status as the number 1 rice exporter will be seriously threatened.

One of the commonly used insecticides in rice for control of rice planthoppers is BPMC or Fenobucarb, a carbamate insecticide. Carbamate insecticides have remained effective and widely used but their continued usage may also lower their toxicities. We compared the city of BPMC on field collected brown planthopper (BPH) populations from different areas using standardized topical application method for the ADB-IRRI Rice Planthopper Project analyzed using the PoloPlus program from LeOra Sotfware.

The results of probit analyses showed the estimated LD50 values for BPMC from 3 locations (Table1). These locations have parallel slopes (X2 = 20.3 p=0.61) ranging from 1.83-2.88, thus their toxicities can be compared. The Jinhua population was 53 times more resistant compared with the most susceptible BPH population of San Pablo, Philippines. Although in China BPMC is now seldom used this higher resistance might be due to its high used in previous years. Vietnam populations were 30-36 times more tolerant than that of San Pablo and the other population in Guilin, China was 15 times more tolerant showing moderate resistance to BPMC. The BPH populations from other locations of the Philippines and in Thailand were only 1.7- 5.8 times more tolerant compared to the San Pablo population showing no resistance or low resistance to BPMC.

Table 1 The relative toxicities and potencies of BPMC on field collected BPH populations in 4 countries.

Locations

LD50 ug/g insect

(95% Fiducial limits)

Slope (+se)

Heterogeneity

Relative potency

San Pablo, Phil

0.835 (0.599-1.055)

2.11 (0.32)

0.73

1

Ang Thong, Th

1.418 (1.099-1.744)

2.06 (0.23)

0.55

1.70

Pila2, Phil

1.643 (0.905-2.256)

2.88 (0.43)

1.27

1.97

Pila1 , Phil

1.762(1.209-2.387)

2.87 (0.30)

1.28

2.11

Nakhon Ratchasima,Th

1.904 (1.545-2.271)

2.49 (0.29)

0.15

2.28

Pila, Phil

2.146 (1.683-2.612)

2.63 (0.32)

0.39

2.57

IRRI,Phil

2.185 (1.815-2.573)

2.91 (0.32)

0.87

2.62

Isabela, Phil

3.685 (2.095-5.447)

2.05 (0.25)

1.10

4.41

Nueva Ecija, Phil

4.877 (3.773-6.084)

2.18 (0.29)

0.09

5.84

Guilin, China

12.848 (8.221-18.072)

2.13 (0.20)

1.69

15.38

Long An, Viet

25.450 (18.353-42.190)

1.83 (0.42)

0.18

30.46

Tien Giang, Viet

30.436 (21.890-54.325)

1.83 (0.44)

0.47

36.43

Jinhua, China

44.792 (24.248-61.856)

2.46 (0.34)

2.13

53.61

In Table 2, were the other group of locations that parallel slopes (X2 = 1.13, p= 0.95) ranging from 1.49 – 1.82. the was Changsha, China population which was most resistant (48 times) followed by Davao, Philippines (45 times) indicating that considerable resistance have developed in The BPH population in Vietnam showed moderate resistance (36 times) to BPMC. The other two populations from Bicol and IRRI, Philippines showed low resistance and were only 12 times and 7.86 times more tolerant, respectively, as compared to the most susceptible population in Chainat, Thailand.

Table 2 The relative toxicities and potencies of BPMC to BPH populations of 6 different locations

Locations

LD50 ug/g insect

(95% Fiducial limits)

Slope (+se)

Heterogeneity

Relative potency

Chainat, Thailand

0. 634 (0.370-0.936)

1.65 (0.16)

1.62

1

IRRI, Philippines

4.981 (3.589-6.699)

1.65 (0.26)

0.56

7.86

Bicol, Philippines

7.635 (5.829-9.927)

1.68 (0.23)

0.23

12.04

An Giang, Vietnam

22.939 (17.473-34.883)

1.81 (0.33)

0.09

36.17

Davao, Philippines

28.541 (21.028-43.071)

1.82 (0.39)

0.66

45.01

Changsha, China

30.456(22.612-40.494)

1.49 (0.22)

1.00

48.03

The trend in toxicity of BPMC to China, Davao, Philippines and Vietnam populations is comparable to those reported by Matsumura et al (2008). Moreover, a cross-resistance of with similar modes of actions and other insecticide cl such as pyrethroids has been reported by Chung et al (1981) in Taiwan BPH populations. Thus the cypermethrin, a pyrethroid, which is also applied in the collection sites in Davao might have induced possible cross-resistance of Davao BPH population to BPMC. However, the IRRI population has only acquired a low resistance of 1.5 times to 3.6 times to BPMC as compared to the relative toxicity study by Fabellar and Heinrichs (1986). The resistance could be due to high usage of carbamates and organophosphates that have the same mode of action. Insecticide mixtures like Brodan (BPMC + Chlorpyrifos) is commonly used against rice pests in the collection sites in Luzon area.

In Iloilo, planthopper outbreaks have damaged about 6700 ha and 2700 ha have suffered significant yield losses. Damages in Iloilo were much higher than outbreaks in Capiz and other areas reported earlier (Read: Outbreaks in Philippines). We conducted a survey of 33 farmers in 3 barangays in Iloilo and found that 18 farmers’ fields (54%) had hopperburn symptoms. The farms where hopperburn had occurred were mostly planted with PSB Rc 120. The degree of damages varied from low (1-10%) in 8 fields, medium (30-50%) in 2 fields, and high (70-90%) in 2 fields. Six more farmers had hopperburn but could not estimate the extent of loss.

The two fields with 70-90% infestations were sprayed 5 times with cypermethrin insecticides starting from 15 days after transplanting with subsequent spray applied at weekly intervals. Other fields were yellowing due to high hopper densities were also sprayed with cypermethrin between 2 to 5 times. The risk value for cypermethrin is moderate but when applied 5 times, the fields could be 5 times more vulnerable (Read: Assessing BPH outbreak risks).

Relationship between yields and number of insecticide sprays

The yields of farmers with 1 to 6 insecticide sprays were not significantly different although there was a general negative relationship. (Read: Do insecticides increase yields?). Yields varied from 1 to 8 t/ha and the farm that used only 1 spray yielded 8 tons, while the farm that used 5 sprays had only 1 ton because of hopperburn.